Plant breeding is a numbers game. The more trees you have, the better your chances of finding one that has the desired combination of genes. Though we plant 150 trees from each family line in our seed orchard plots, these seedlings can die from a variety of causes – predation, bad weather, mechanical damage, competition from other seedlings – before we ever have a chance to evaluate them for blight resistance. That is why we consider it important to prevent loss, especially in the first year.
Last year, after bad weather and other problems caused major losses in the Maryland chapter’s seed orchards, we decided that, beginning in 2017, we would raise spare seedlings in pots to replace any in our orchards that fail to germinate or die early in their first season. We grew 10-20% more seedlings for each family line than we had space for in our orchards.
The project has paid off. The Maryland chapter planted 2,768 nuts in 2017 to create new seed orchard plots or complete partial plots planted in previous years. Of these, 11% had failed to sprouted into seedlings by late May. By filling 283 vacant positions with new seedlings from the right family lines, we were able to bring our newest seed orchard plantings to over 99% capacity. We could easily have achieved 100% capacity had we not lost some seeds over the winter to storage molds.
Growing spare trees in pots appears to be well worth the minimal effort, space and expense required. If carried through until inoculation, the 10% increase we just achieved in our selection population will significantly improve the probability of finding highly-resistant trees in the coming years.